It is well-known that devices such as hormonal or copper intra-uterine devices (IUD), which are used as a common method of anti-conception and/or for treatment of menorrhagia, have a string attached to the device. Similarly, tampons also have a withdrawal cord, which is affixed to the tampon by making a knot in said cord. After insertion of a T-shaped IUD, the string remains positioned within the cervix for a period of 5 to 10 years to facilitate extraction of the IUD by the health care provider. It is customary to provide the string of an IUD with a knot to securely fasten the string.
During the history of development of Cu-IUD, specific attention has been brought on the thread and on the knot. The Dalkon Shield tails experience in US in the 1970s established that pelvic infection (which could ultimately lead to death of the woman) may be attributed to the multifilament thread connected to the device. Ever since, the field has been more cautious about the details of the string and knot connected to medical devices. More specifically, the knot should not hamper the correct insertion of the device, it should not hamper the efficacy of the device nor should it have a negative impact on the safety of the device. In addition, it should be durable enough to allow for a correct removal of the device after several years.
The type, the positioning, the resistance, the strength of attachment and the stability all over the duration of use of the device may have great impact on the global quality of the device. The manufacturing of a device of adequate quality imposes a close control of all these parameters and a high reproducibility in the process of making the knot. Typical examples are the copper- or hormone (e.g. levonorgestrel) based IUDs. In this case, the length of string between knot and IUD is crucial as well as the type and thickness of the knot, because the knot can block the delivery of the IUD when e.g. applied through an applicator tube or device.
Furthermore, the type, the positioning, the resistance and the thickness of the knot are of crucial importance for the correct use of the device at the insertion step or at the removal steps. In addition, the strength of the attachment of the flexible element to the IUD is influenced by the form of the knot.
Finally, the position of the knot with respect to the IUD and its form and thickness will also be important to avoid spreading of possible infectious agents such as viruses, bacteria and fungi from the vaginal region into the uterus, since it has been observed that said knot can be the thriving place of infectious agents (cf. e.g. Roberts at al., 1984, Contraception 29(3):215-28; Rivera at al., 1993, Curr Opin Obstet Gynecol 5(6):829-32).
Currently, the flexible elements or wires are mostly tied manually to the IUDs, because of the importance to have a reproducible knot at the correct position. A drawback of presently known methods for making such knots is that they are too slow and labor-intensive. Furthermore, they are prone to human error and batch to batch differences.
Some methods of automating the knot-forming process are known for e.g. tampons. However, they are all quite complex. We refer for example to U.S. Pat. Nos. 4,836,587 and 5,566,435, describing an apparatus to knot tampon strings using rather complex devices. The present invention provides an alternative device and method to make knots in flexible elements of medical devices or medical devices containing drugs, which is easy to handle, cheap and very effective in positioning and shaping of the knot vis-à-vis the device.